I've got an audigy 1, no problems here.
Use the 'genkernel' config to compile your kernel, and
emerge hotplug ; rc-update add hotplug default
Which should make it auto-load the modules, you will
also probably want to rc-update add alsasound default
to make sure the oss emulation stuff gets set up...
Anyhow, that'll give you a starting point.

Then use 'alsamixer' to turn up the volume levels on everything,
and play a .WAV file with aplay to verify it's working at a console
level before you try it inside of X/GNOME/KDE.